What this actor is
The Russian-led collective security organisation whose only Caucasus member has frozen its participation, stopped paying, and said publicly it would be glad to be expelled — leaving the alliance holding a membership it can neither enforce nor end without conceding the point.
Confidence: High Reviewed 2026-09-01
What the organisation is here
In this module the CSTO is not a force, a deployment or a planning structure — it is a membership status, and the dispute over it is a diplomatic file rather than a military one. Vigil publishes nothing about its command arrangements, exercises or capabilities, because nothing in this module turns on them.
The standoff
Armenia froze participation in February 2024 after concluding the alliance had not acted for it, and by August 2026 the prime minister said he had no intention of resuming and would be glad if Armenia were expelled. That inverts the usual cost of rupture: Armenia does not pay the price of withdrawing, and the organisation must either expel — doing the thing Yerevan says it wants — or not, in which case its Article 25 warning is shown to be unenforceable. Neither has happened.
What has not changed
Armenia remains a de jure member and has not lodged a withdrawal. The Russian base at Gyumri sits on a lease to 2044 under a separate bilateral arrangement that the CSTO question does not govern, and Armenia has not proposed changing it. Reading the freeze as a departure, or the retained membership as continuity, are both wrong.
Not published for Collective Security Treaty OrganizationPosture (objectives, constraints, leverage)
Elsewhere in Caucasus
Last reviewed — 2026-09-01